One who uses the Bible to attack/defame others' characters instead of as a guide to proper living. These people tend to be depressingly ignorant of anything else except the Bible and behavior as expected by the religious.

That Bible Thumper makes me so sick! Every day, he stands on my porch shouting about how I'm doomed to a flaming eternity in Hell just because I watch Crank Yankers and South Park!

Originating from typically southern US fundamentalist Christian sects given to evangelizing in a very outgoing, rumbunctious way, often characterized by a religious bigot standing on a street corner, with or without foam around his mouth, shouting about how we should all turn to Christ, whilst vigourously thumping his soft covered bible for emphasis.
Their actions usually do more harm than good to their cause and bring into disrepute and ridicule those more reticent Christians.

He's a bible thumper, so don't go near him.
He thinks everything in the bible should be taken literally; he's a foolish bible thumper.

The Urban Dictionary T-Shirt

An extremely fanatical religous zealot,
often characterized by their constant refences to the bible and their intent on converting everyone in a 100 mile radius.
They are essentially the same as Islamic fundamentalists, with the same religous zeal and fantacism.
"Hands that help are far better than lips that pray."

1. Religous Fundamentalist are contributing to the partisan bickerings that are hurting America.

The Urban Dictionary T-Shirt

a christian male or female whos view of right and wrong is completely out of wack.believes that every single thing in the bible is a law to be followed or you go to hell.(im christian, but these biblethumpers are just psycotic)

i bet a bible thumper would read that part of the bile that says you can enslave your family and would do it.

bible thumper:you cant watch south park!its against christianity!!your going to hell!
me:dude, where does it say in the bible i cant watch a tv show?